THE idea of moving objects with the power of the mind has fascinated mankind for millennia. At first it was the province of gods, then sorcerers and witches. In the late 19th century psychokinesis, as the trick then came to be known, became a legitimate object of study, as part of the nascent field of parapsychology, before falling into disrepute in the arch-rationalist 20th century. Since the 1990s, however, it has seen something of a revival, under a more scientifically acceptable guise.

There is nothing particularly magical about moving things with thoughts. Human beings perform the feat every time they move a limb, or breathe, by sending electrical impulses to appropriate muscles. If these electrical signals could be detected and interpreted, the argument goes, there is in principle no reason why they could not be used to steer objects other than the thinker's own body. Indeed, over the past two decades brain-computer interfaces (BCIs) which use electrodes implanted in the skull have enabled paralysed patients to control computer cursors, robotic arms and wheelchairs.

Now, though, non-invasive BCIs, where electrodes sit on the scalp instead of burrowing through it, are finally becoming a realistic alternative to the complicated surgical procedure that implants necessitate. Electroencephalography (EEG), which measures electrical activity along the scalp, has long been used clinically to diagnose epilepsy, comas and brain death, and as a research tool in neuroscience and cognitive psychology. Last year an Austrian company called Guger Technologies released a system that uses EEG to allow paralysed patients to type. The system highlights letters one by one on a grid. When the desired letter comes up an EEG headset picks up the brain activity associated with recognising it. At five to ten characters per minute the process is slow and laborious, but it offers patients a way to communicate with others. The device can also be used to attract a minder's attention, to get a computer to read out a text or to send commands to external devices such as a TV.

Follow the jumping blue dot

A team at the University of Zaragoza, in Spain, led by Javier Minguez, has developed some promising prototypes using similar principles. One is a wheelchair that generates a 3D map on a screen. A blue dot jumps between places on the map and when it hits the desired destination, the EEG electrodes pick this up and steer the wheelchair towards it. Another lets severely disabled patients use a real-time video camera connected to the internet, allowing them, for instance, to attend a family reunion virtually. Dr Minguez is also part of a group developing a robot arm that could help patients reach for a drink or feed themselves. The University of Zaragoza has set up a spin-off to commercialise the research and Dr Minguez expects a fully fledged device by 2014.

The number of electrodes needed to get useful EEG results is steadily decreasing. Several EEG devices have been released in recent years sporting fewer sensors than the high-end kit, notably for use in video gaming. In May an organisation called Thought-Wired, based in New Zealand, showed off a system that uses a commercially available 14-sensor headset called the Emotiv EPOC, which costs around $300 and was designed with gaming in mind, as a smart-home controller. It enables disabled people to control lights, make phone calls, operate air conditioners and perform other simple tasks.

Early efforts to use rudimentary headsets for computer games were not exactly riveting. Two headset-based toys released in 2009—Uncle Milton's Star Wars Force Trainer and Mattel's Mindflex—used players' concentration and relaxation levels, gauged by comparing brain waves of different frequencies, to make a ball rise or fall using airflow from a fan.

Since then, however, headset prices have tumbled, leading to several niftier offerings. For instance, researchers in Germany have used Emotiv's headset to build a device which allows a driver to tell a car to go left or right, accelerate or slow down by thinking about it. In July Toyota unveiled a concept bicycle, the PXP, with a thought-controlled gear-shift mechanism.

Meanwhile, a British company called Myndplay is creating short interactive films in which viewers step into the shoes of the protagonists and influence the plot by focusing or relaxing. Mohammed Azam, Myndplay's boss, thinks the technology has potential beyond entertainment. For example, he has been working on an app in which users must keep their cool in various dating scenarios. Other projects include training for job interviews and a virtual-therapy app to help treat stress and phobias. Myndplay will unveil its latest product at the Tokyo Games Show on September 15th.

In April NeuroSky, a Californian maker of EEG headgear, launched its $100 MindWave headset, which reduces the number of sensors to just one. This is possible using algorithms that filter out interference caused by external electrical activity. The American Olympic archery team has used the company's technology to help athletes gain and retain composure. B-Bridge International, NeuroSky's partner, has launched BrainAthlete, a golf visor equipped with two EEG sensors. It lets players plot their concentration levels at important moments in a game—during a golf swing, say—on a chart and, in so doing, helps them learn to ignore distractions.

There are some decidedly frivolous applications for EEG technology, too, such as a pair of cat ears on a hairband that stand up when the wearer is concentrating and lie down when he or she is relaxed. Videos of the one-off toy proved such a hit online that its Japanese creator, Neurowear, is considering mass production.

Not all fun and games

On a more serious note, earlier this year Myndplay games and interactive films were used as part of a scheme to reduce reoffending rates and anti-social behaviour among prison inmates aged 18 to 25. “We found it to be an excellent tool to show them how they can develop greater control over their thought processes,” says David Apparicio, a magistrate who spearheaded the programme, called Chrysalis. He hopes to commission customised content to test young offenders' reactions in scenarios such as being challenged to a fight or invited to commit a crime.

Simpler sensors: Headsets from Emotiv (above) and NeuroSky (below)

SpeedMath, a game that comes with the NeuroSky headset, shows students which types of task require most mental effort on their part, with the aim of encouraging more focused work. Jack Mostow, a researcher at Carnegie Mellon University in Pittsburgh, has used NeuroSky's headsets to distinguish between the patterns of brain activity involved in reading easy and difficult sentences. This, he thinks, means that EEG could be used to tailor teaching to pupils' needs.

Market-research companies, too, have jumped on the BCI bandwagon. Proponents of the newish field of neuromarketing trumpet non-invasive BCI as a way for companies to gain insights into how consumers perceive their products, packaging or advertisements. In March NeuroFocus, another California-based outfit, demonstrated what it claims is the first medical-grade dry EEG headset. The company, which was recently bought by Nielsen, a big research firm, has been using conventional EEG devices (which require gooey conductivity gels), in its neuromarketing activities for around five years. Mynd, the firm's new wireless headset, will have between 32 and 64 sensors, and will begin commercial use from September. A.K. Pradeep, the company's boss, says that by measuring attention, engagement and memory retention, its equipment can gauge purchase intent, novelty factor and comprehension of an advertisement.

Others dismiss neuromarketing as junk science, at least for now. Although there is evidence that EEG-based metrics can reflect cognitive processes of interest to marketers, says Phil Harris, who lectures on neuromarketing at the University of Melbourne, no published evidence so far indicates that portable dry-electrode systems offer a reliable glimpse of these processes. The Advertising Research Foundation (ARF), an industry body, recently carried out an evaluation of neuromarketing technologies. NeuroFocus and EmSense, another company that uses dry EEG headsets in market research, declined to take part. Dr Pradeep says he thinks the methods the ARF used in its appraisal were flawed. The eight companies that did participate, which were asked to analyse a campaign for a toothpaste brand, came up with widely varying conclusions.

Mind-blowing

Artists using BCI face no such niggles. At the FutureEverything festival, which was held in May in Manchester, Marcos Lutyens created an interactive multimedia installation which converted EEG readings of people drinking vodka cocktails into colourful, real-time visual displays. Chris Meyer, a graphic designer from California, has used the technology to modify his Nerf gun so that he can shoot foam bullets using thought alone. Others have gone even further. One group of artists from Toronto used a NeuroSky headset connected to a gas canister to generate seven-metre (23-foot) flames.

As might be expected, not everyone shares the enthusiasm for supplanting mankind's traditional, arm's length relationship with technology with a deeper, BCI-mediated sort. Jens Clausen, a medical ethicist at Tübingen University, warns that excessive use of BCI for gaming could alter brain activity in ways that conventional gaming does not, and that as yet are poorly understood. And blurring the distinction between thinking about an act and actually performing it raises some tricky moral and philosophical questions.

Yet as it stands, the technology seems poised for a period of rapid development which both the needy and thrill-seekers are bound to greet with cheers. As Tan Le, co-founder of Emotiv, the headset-maker, told the TED conference last year, “We are only really scratching the surface of what is possible.” Those scratches are, however, getting deeper all the time.